1. Field of the Invention
The present invention relates to a method of cleaning work pieces, such as semiconductor wafers, and, more particularly, to a method of removing debris from cleaning pads used to clean the work pieces.
2. Description of Related Art
Semiconductor wafers are subjected to various processing steps during fabrication. Such processing steps include growth or deposition of insulating layers, deposition of conductive layers, doping with one or more impurities, planarization, and other steps known to the skilled artisan. A high level of wafer cleanliness is required to be maintained during the fabrication process. As a result, many of the processing steps are either preceded or proceeded by one or more cleaning steps to ensure the appropriate level of wafer cleanliness is maintained.
Wafer cleaning, especially after a wafer planarization process, such as chemical-mechanical planarization (CMP), involves cleaning the wafer surface with a cleaning pad, brush, or sponge. This cleaning process removes various forms of debris, such as particulate, residue, and other contaminants remaining on the wafer surface after the CMP process. Following the wafer cleaning process, especially following a post-CMP process cleaning, much of this debris is adhered to, and may be embedded in, the cleaning pads. If the concentration of the debris collected by the cleaning pads becomes sufficiently high, the collected debris may cause damage to wafers that are subsequently cleaned using the same cleaning pads.
Naturally, from an economic standpoint it is desirable that the wafer fabrication process be conducted rapidly, efficiently, and with a high volume throughput. Thus, it is desirable to have a process for rapidly and efficiently removing the debris collected by the cleaning pads during the wafer cleaning process so that wafer damage can be prevented. Furthermore, it is desirable that the process used to remove the debris from the cleaning pads be fully integrated into the wafer fabrication process and processing equipment.
Presently, wafer cleaning apparatuses and methods employ so-called xe2x80x9cbeater barsxe2x80x9d or use filler wafers to remove the debris from the cleaning pads. If a beater bar type of pad cleaner is used, debris is removed from a cleaning pad by compressing the cleaning pad against a beater bar, in a separate fluid bath, and rotating the pad. Such a system requires the construction and use of a separate pad cleaning station, in addition to the other wafer conditioning stations within the equipment. Thus, this system impacts overall system throughput and complexity, thereby increasing overall system costs. The use of filler wafers also adversely affects system throughput, since the normal wafer process must be stopped in order to process the filler wafers. Yet another alternative is to simply replace the cleaning pads periodically. This alternative also adversely affects throughput and overall cost.
Hence, there is a need in the art for a method of removing debris from the cleaning pads in work piece cleaning equipment that improves upon the drawbacks noted above. Namely, a method of removing debris that does adversely affect work piece throughput by requiring either a separate pad cleaning station, use of separate filler wafers, or frequent, periodic replacement of the cleaning pads.
The present invention provides a method for removing debris from cleaning pads used in work piece cleaning equipment that does not require a separate station or system for removing debris from the cleaning pads, does not require the use of special filler wafers to remove the debris therefrom, nor requires frequent replacement of the cleaning pads.
In one aspect of the present invention, a method of removing debris from cleaning pads in a work piece cleaning apparatus includes a compression force application and removal step and a rinsing step. The compression force application and removal step includes cyclically applying and removing a compression force to cause a first cleaning pad to compress against a second cleaning pad. The cyclical application and removal of the compression force occurs for a predetermined number of force application/removal cycles. The rinsing step comprises applying a rinsing fluid to the first and second cleaning pads.
In another aspect of the invention, a method of cleaning a work piece includes bringing a first surface of the work piece into contact with a first cleaning pad, and bringing a second surface of the work piece into contact with a second cleaning pad. In the presence of a cleaning fluid, one or more of the first and second surfaces of the work piece are cleaned with the first and second cleaning pads. The work piece is removed from contact with the first and second cleaning pads, and the cleaning pads are thereafter cleaned. The process of cleaning the cleaning pads includes a compression force application and removal step and a rinsing step. The compression force application and removal step includes cyclically applying and removing a compression force to cause a first cleaning pad to compress against a second cleaning pad. The cyclical application and removal of the compression force occurs for a predetermined number of force application/removal cycles. The rinsing step comprises applying a rinsing fluid to the first and second cleaning pads.
Other features and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the present invention.